Electrostatic chuck electrical balancing circuit repair

ABSTRACT

The present invention includes methods and apparatus for repairing an electrical connection between bipolar electrodes contained within an electrostatic chuck and a conductive mask disposed atop the electrostatic chuck, known as a balancing circuit. Embodiments of the invention are particularly useful after removal of an electrostatic chuck for refurbishment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to apparatus andmethods for repairing a severed electrical connection in the balancingcircuit of an electrostatic chuck.

2. Description of the Related Art

In substrate processing equipment, an electrostatic chuck is commonlyused for clamping a substrate to a pedestal during processing. Theelectrostatic chuck clamps the substrate by creating an attractive forcebetween the substrate and the chuck. A voltage is applied to one or moreelectrodes in the chuck to induce oppositely polarized charges in thesubstrate and the electrodes, respectively. The opposite charges pullthe substrate against the chuck, thereby retaining the substrate.

In a bipolar, electrostatic chuck, a chuck body has a pair of coplanarelectrodes embedded therein. Each electrode is respectively connected toa terminal of a dual power supply having a common terminal, which isreferred to as a center tap. The center tap is connected to a substratespacing mask provided on the surface of the chuck in order to balanceany variations in the impedance between the substrate and theelectrodes. Thus, a constant electrostatic attraction force between thesubstrate and the chuck is maintained across the surface of the chuck.

The electrical connection between the center tap and the substratespacing mask is often made through the conductive wall of a gas conduitused to supply gas to the backside of the substrate during processing.The gas conduit is attached to a metalized central bore within the chuckbody. This connection works well during substrate processing, but theconductive connection is sometimes disrupted or otherwise compromisedduring the process of removing and refurbishing the electrostatic chuckassembly.

Therefore, a need exists for apparatus and methods of restoring acompromised balancing circuit electrical connection in an electrostaticchuck assembly.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a substrate support assemblycomprises an electrostatic chuck having an electrode embedded thereinand having an aperture disposed therethrough, a conductive linerdisposed on the surface of the electrostatic chuck within the aperture,a conductive tubing extending from a lower surface of the electrostaticchuck and axially aligned with the aperture, and a conductive insert atleast partially within the aperture and at least partially within theconductive tubing. In one embodiment, the conductive insert provides aconductive path between the conductive liner and the conductive tubing.

In one embodiment, a method for repairing a severed electricalconnection within a balancing circuit of an electrostatic chuck assemblycomprises determining the resistance between a substrate spacing maskdisposed on the upper surface of an electrostatic chuck and a conductivetubing extending from the lower surface of the electrostatic chuck andaxially aligned with a metallically lined aperture extending through theelectrostatic chuck, evaluating the determined resistance to determinewhether the electrical connection between the conductive conduit and thesubstrate mask has been severed, and repairing the severed connection byrestoring a conductive path between the conductive tubing and thesubstrate spacing mask by using a welding technique to re-melt andre-fuse conductive material located between the metallically linedaperture and the conductive tubing. In one embodiment, the weldingtechnique is selected from the list consisting of electron beam welding,laser welding, and micro plasma welding.

In one embodiment, a method for repairing a severed electricalconnection within a balancing circuit of an electrostatic chuck assemblycomprises determining the resistance between a substrate spacing maskdisposed on the upper surface of an electrostatic chuck and a conductivetubing extending from the lower surface of the electrostatic chuck andaxially aligned with a metallically lined aperture extending through theelectrostatic chuck, evaluating the determined resistance to determinewhether the electrical connection between the conductive conduit and thesubstrate mask has been severed, and placing a conductive insert intothe aperture to repair the severed connection and restore a conductivepath between the conductive tubing and the substrate spacing mask.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic, cross-sectional view of an exemplary substratesupport assembly, which may benefit from the present invention.

FIG. 2 is a schematic depiction of a substrate support assemblyutilizing a method of repairing a severed electrical connection betweena conductive gas conduit and a conductive passage according to oneembodiment of the present invention.

FIG. 3 is a schematic, cross-sectional view of a substrate supportassembly utilizing a method of repairing a severed electrical connectionbetween a conductive gas conduit and a conductive passage according toanother embodiment of the present invention.

FIG. 4 is a side view of a “butterfly” spring used in one embodiment ofthe present invention.

FIG. 5 is a schematic, cross-sectional view of a substrate supportassembly comprising another embodiment of the present invention.

DETAILED DESCRIPTION

The present invention includes methods and apparatus for testing andrepairing an electrical connection between bipolar electrodes containedwithin an electrostatic chuck and a conductive mask disposed atop theelectrostatic chuck, particularly after removal of the electrostaticchuck. This connection is known as a balancing circuit because itbalances the electrostatic forces applied to a substrate positioned atopthe electrostatic chuck.

In one embodiment, the electrostatic chuck is tested to determinewhether the balancing circuit electrical connection has been disrupted.In one embodiment, if the electrical connection has been disrupted, theelectrical connection is repaired via a welding process. In oneembodiment, if the electrical connection has been disrupted theelectrical connection is repaired with a conductive insert.

FIG. 1 is a schematic, cross-sectional view of an exemplary substratesupport assembly 100, which may benefit from the present invention. Thesubstrate support assembly 100 includes an electrostatic chuck 105 forsupporting and retaining a substrate 102 during processing.

The electrostatic chuck 105 has a substrate spacing mask 107 disposed onthe upper surface thereof. The substrate spacing mask 107 may comprise amaterial such as titanium, titanium nitride, or diamond-like carbon, andthe like. The spacing mask 107 is deposited to a pre-defined thicknessthat maintains the substrate 102 slightly above the surface of theelectrostatic chuck 105. The electrostatic chuck 105 further contains aconductive passage 103 disposed therethrough. In one embodiment, theconductive passage 103 has a conductive coating, such as copper silversolder material, that electrically couples the spacing mask 107 to thebottom region of the electrostatic chuck 105.

In one embodiment, a heat transfer fluid is transported from a gassource 130 to a conductive gas conduit 132 through a gas conduit 135.The conductive gas conduit 132 is mechanically and electrically coupledto the conductive passage 103, such as by brazing. In one embodiment,the conductive gas conduit 132 is conductive tubing, such as stainlesssteel tubing. In one embodiment, the conductive gas conduit is axiallyaligned with the conductive passage 103. Heat transfer fluid istransported through the conductive gas conduit 132 to the passage 103extending through the electrostatic chuck 105. The gas is furthertransported through the conductive passage 103 to the backside of thesubstrate 102. The flow of gas may provide heating or cooling to thebackside of the substrate 102. The heat transfer gas may be helium,argon, hydrogen, carbon tetrafluoride, or the like.

The electrostatic chuck 105 includes one or more chucking electrodes 110embedded therein. The electrodes 110 are fabricated from a conductivematerial, such as tungsten, graphite, copper, or the like. The chuckingelectrodes 110 are disposed in an upper region of the electrostaticchuck 105 to provide the necessary electrostatic force to retain thesubstrate 102. The electrodes 110 may be configured in any mannernecessary to retain the substrate 102. However, the embodiment depictedin FIG. 1 is a bipolar configuration.

The electrodes 110 are connected to a power supply 140 comprising a pairof dual terminal DC voltage supplies 162 and 164 with a center tap 166.The cathode on the voltage supply 162 is coupled to one of the bipolarelectrodes 110 via an electrode lead 163, and the anode from the othervoltage supply 164 is coupled to the other bipolar electrode 110 via anelectrode lead 165. The cathode of the voltage supply 164 is coupled tothe anode of the voltage supply 162 with a center tap 166 coupledtherebetween. The center tap 166 is further coupled to the spacing mask107 via the conductive gas conduit 132 and the conductive passage 103.As such, variations in the electrostatic force due to physicalvariations in the distance between the substrate 102 and the electrode110 may be balanced. Therefore, changes in the electrostatic force arebalanced by having the center tap 166 of the power supply 140 coupled tothe spacing mask 107 in a balancing circuit.

Periodic service and maintenance of the substrate support assembly 100is required during the lifetime of a processing chamber housing theelectrostatic chuck 105. Accordingly, the electrostatic chuck 105 may beperiodically removed from its processing chamber for refurbishing.

However, it has been discovered that the electrical connection betweenthe conductive gas conduit 132 and the conductive passage 103 may becomesevered during removal of the electrostatic chuck 105. Thus, thebalancing circuit between the spacing mask 107 and the electrodes 110 isrendered non-functional.

One embodiment for repairing a severed electrical connection in thebalancing circuit of the substrate support assembly 100 involves firsttesting the assembly to detect whether the connection has been severedand then repairing the severed connection through the use of varioustechniques and/or devices. First, the substrate support assembly istested to determine whether the electrical connection between theconductive gas conduit 132 and the conductive passage 103 has beendisrupted. In one embodiment, the resistance across the connection maybe tested via an ohmmeter. If the resistance is equal to or less than aspecified resistance, the connection is intact. If the resistance isgreater than the specified resistance, the connection must be repaired.In one embodiment, the specified resistance is 200 kΩ. Next, theconnection is repaired.

FIG. 2 is a schematic depiction of a method of repairing the connectionbetween the conductive gas conduit 132 and the conductive passage 103according to one embodiment of the present invention. In one embodiment,the connection is repaired by electron beam welding 200 the connectionto re-melt and re-fuse the braze material used in the connection.Alternatively, laser welding or micro plasma welding may be used tore-melt and re-fuse the braze material used in the connection. In oneembodiment, conductive filler material is added during the welding. Inanother embodiment, a conductive preform is added during the welding.

Electron beam welding 200 is a fusion welding process in which a beam ofhigh-velocity electrons is applied to materials being joined. Theworkpieces melt as the kinetic energy of the electrons is transformedinto heat upon impact, and filler metal, if used, also melts to formpart of the weld. Because the electron beam is tightly focused, thetotal heat input is actually much lower than that of any arc weldingprocess. As a result, the effect of welding on the surrounding materialis minimal, and the heat-affected zone is small. Distortion is slight,and the workpiece cools rapidly. Thus, electron beam welding may be usedto re-melt and re-fuse the severed braze material at the connectionbetween the conductive gas conduit 132 and the conductive passage 103with minimal effect on the electrostatic chuck 105.

FIG. 3 is a schematic, cross-sectional view of the substrate supportassembly utilizing another method of repairing the severed electricalconnection between the conductive gas conduit 132 and the conductivepassage 103 according to another embodiment of the present invention. Aconductive insert 300 is disposed within the conductive passage 103 andspanning the connection between the gas conduit 132 and the conductivepassage 103. The conductive insert 300 is positioned such thatconductive contact is made between the conductive passage 103 and theconductive insert 300 as well as between the interior of the conductivegas conduit 132 and the conductive passage 103 via the conductive pathprovided by the conductive insert 300.

In one embodiment, the conductive insert 300 is a “butterfly” spring400, a schematic depiction of which is shown in FIG. 4. The butterflyspring 400 may comprise a torsion spring portion 405 with end portions410 extending therefrom. In one embodiment, the butterfly spring 400 maycomprise a conductive wire, such as nickel containing iron alloys,superalloys, or copper wire, helically coiled as shown in FIG. 4. In oneembodiment, the conductive wire is operable at a temperature range fromabout 100° C. to about 500° C. The end portions 410 may be helicallycompressed and inserted into the conductive passage as shown in FIG. 3such that when released, the end portions make electrical contactbetween the conductive gas conduit 132 and the conductive passage 103.

FIG. 5 is an enlarged, schematic, cross-sectional, partial view of thesubstrate support assembly 100 comprising another embodiment of aconductive insert 500. The conductive insert 500 comprises a plug member505 with a canted coil spring 510 positioned thereabout. The canted coilspring 510 comprises a conductive material, such as stainless steel. Theplug member 505 may be comprised of a non-metallic material, such asquartz, having one or more gas passages 506 disposed therethrough. Inone embodiment the gas passages 506 may be configured at one or morenon-perpendicular angles with respect to the top and bottom surfaces ofthe plug 505. In one embodiment, the plug 505 may have an annular groove508 circumscribing the plug 505. The canted coil spring 510 may beconfigured around the plug 505 and at least partially disposed withinthe annular groove 508.

In order to repair the connection between the conductive gas conduit 132and the conductive passage 103, the conductive insert 500 may beinserted into the conductive passage 103, wherein the conductive cantedcoil spring 510 makes electrical contact with both the conductive gasconduit 132 an the conductive passage 103. Thus, the balancing circuitof the substrate support assembly 100 is restored by the conductiveinsert 500, which provides a path for electrical current between theconductive gas conduit 132 and the conductive passage 103.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A substrate support assembly, comprising: an electrostatic chuckhaving an electrode embedded therein and having an aperture disposedtherethrough; a conductive liner disposed on the surface of theelectrostatic chuck within the aperture; a conductive tubing extendingfrom a lower surface of the electrostatic chuck and axially aligned withthe aperture; and a conductive insert at least partially within theaperture and at least partially within the conductive tubing, whereinthe conductive insert provides a conductive path between the conductiveliner and the conductive tubing.
 2. The substrate support assembly ofclaim 1, wherein the conductive insert comprises a conductive spring. 3.The substrate support assembly of claim 2, wherein the conductive springcomprises a torsion spring portion with elongated end portions extendingtherefrom.
 4. The substrate support assembly of claim 2, wherein theinsert further comprises a non-metallic plug having an apertureextending therethrough.
 5. The substrate support assembly of claim 4,wherein the aperture is configured at non-perpendicular angles withrespect to a top and bottom surface of the non-metallic plug.
 6. Thesubstrate support assembly of claim 1, wherein the conductive insertcomprises: a non-metallic plug having an aperture extending therethroughand an annular groove circumscribing an external surface of the plug;and a conductive spring at least partially contained within the annulargroove.
 7. The substrate support assembly of claim 6, wherein the plugcomprises quartz and the conductive spring is a canted coil spring. 8.The substrate support assembly of claim 1, wherein the conductive liningis electrically coupled to a substrate mask disposed on an upper surfaceof the electrostatic chuck.
 9. A method for repairing a severedelectrical connection within a balancing circuit of an electrostaticchuck assembly, comprising: determining the resistance between asubstrate spacing mask disposed on the upper surface of an electrostaticchuck and a conductive tubing extending from the lower surface of theelectrostatic chuck and axially aligned with a metallically linedaperture extending through the electrostatic chuck; evaluating thedetermined resistance to determine whether the electrical connectionbetween the conductive conduit and the substrate mask has been severed;and repairing the severed connection by restoring a conductive pathbetween the conductive tubing and the substrate spacing mask by using awelding technique to re-melt and re-fuse conductive material locatedbetween the metallically lined aperture and the conductive tubing,wherein the welding technique is selected from the list consisting ofelectron beam welding, laser welding, and micro plasma welding.
 10. Amethod for repairing a severed electrical connection within a balancingcircuit of an electrostatic chuck assembly, comprising: determining theresistance between a substrate spacing mask disposed on the uppersurface of an electrostatic chuck and a conductive tubing extending fromthe lower surface of the electrostatic chuck and axially aligned with ametallically lined aperture extending through the electrostatic chuck;evaluating the determined resistance to determine whether the electricalconnection between the conductive conduit and the substrate mask hasbeen severed; and placing a conductive insert into the aperture torepair the severed connection and restore a conductive path between theconductive tubing and the substrate spacing mask.
 11. The method ofclaim 10, wherein the conductive insert comprises a conductive spring.12. The method of claim 11, wherein the conductive spring comprises atorsion spring having an elongated portion at each end, wherein oneelongated portion is electrically coupled to the conductive tubing andthe other elongated portion is electrically coupled to the metallicallylined aperture.
 13. The method of claim 10, wherein the conductiveinsert comprises: a non-metallic plug having an aperture formedtherethrough and having a groove circumscribing the plug; and aconductive spring at least partially disposed within the groove.
 14. Themethod of claim 13, wherein the conductive spring provides a conductivepath between the metallically lined aperture and the conductive tubing.15. The method of claim 14, wherein the nonmetallic plug comprisesquartz and the conductive spring is a canted coil spring.
 16. The methodof claim 10, wherein the determining further comprises measuring theresistance between the spacing mask and the conductive tubing via anohmmeter.
 17. The method of claim 16, wherein the evaluating furthercomprises determining whether the resistance exceeds 200 kΩ.